Wiring Basement Sub Panel

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Old 05-03-14, 10:33 PM
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Wiring Basement Sub Panel

Embarking on my first real DIY project involving electrical wiring. Have my code book, my permit and the internet. I am going to wire a 60 amp sub-panel in the basement to supply the branch circuits.

My first question is whether I can use 4-3 NM-B available at my local Home Depot to wire the sub panel? Code book only seems to allow type NM in dry locations?

My second question is about conduit. Based on the layout of the basement and main circuit board I need to run a portion of the wiring outside, but i'm not sure what type and size of conduit to run. Is 1" Schedule 40 PVC okay, or do I need a larger size or schedule 80? The code book seems a bit vague here. I don't think it's an area where I would need to protect against physical damage (requiring schedule 80), but the code book doesn't really define those locations.

Thanks in advance for your help!
 
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Old 05-03-14, 10:53 PM
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A basement is a dry location. For a 60 amp feed you would use 6-3 not 4-3 NM-b.
Based on the layout of the basement and main circuit board I need to run a portion of the wiring outside, but i'm not sure what type and size of conduit to run.
You can not run NM-b outside in conduit. (Conduit is considered a wet location. if outside) Best practice is to run individual conductors in conduit. Use two #6 black THWN (or red and black), one #6 white, and one #10 green. 1" conduit is okay. Ask your inspector if schedule 80 is needed. It's his judgement that counts. Use a 4x4 box in the basement to transition from NM-b to conduit and THWN.

Not asked but if in the same structure you can use a main lug panel with no disconnect and no ground rod required. You will have to add a bonded ground bar to the panel for the EGC and isolate the neutral bar.
 
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Old 05-03-14, 11:14 PM
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Okay I see that here in the book. 75C THWN 6 AWG is rated for 65 amps. So I need three lengths of THWN or THHN.

These cables will power the main lug panel in the basement, so I don't have any need to transition from NM-B to THWN. I can run THWN from the main panel in the garage to the main lug sub-panel in the basement right?
 
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Old 05-04-14, 12:14 AM
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So I need three lengths of THWN or THHN.
No, four and outside it must be THWN. However most of the time it is dual rated THWN/THHN (THHN is dry location only.)

My previous post:
Use two #6 black THWN (or red and black), one #6 white, and one #10 green.
These cables will power the main lug panel in the basement
THWN is not cable. It is wire. If the garage is detached then my instructions are wrong. If you have room in the subpanel for more than six circuits you will need a disconnect. Also in that case a ground rod is required. Is it detached?
 
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Old 05-04-14, 12:34 AM
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The garage is attached, so everything is within the same structure. So i need four runs of #6 THWN. Now with regards to the conduit, does the entire run of the wire need to be enclosed in the conduit, or just the portion exposed on the side of the house? The entire run goes from the main panel up into the attic, down out of the attic into conduit on the exterior of the house and finally into the basement and attached to the sub panel.
 
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Old 05-04-14, 05:47 AM
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Individual conductors are installed in a complete conduit system. They cannot be run in free air.
 
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Old 05-04-14, 09:49 AM
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The garage is attached, so everything is within the same structure. So i need four runs of #6 THWN.
No, three #6 one #10 ground.
does the entire run of the wire need to be enclosed in the conduit,
If you use (6-3 with ground) NM-b inside and run it protected such as in a wall or attic it does not need conduit.. NM-b is usually easier to run. That is why I suggested cable inside transitioning to THWN in conduit outside.
 
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Old 05-04-14, 03:03 PM
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Okay got it. So my plan is to run 1" Rigid PVC Conduit, Schedule 40 from the main panel in the garage to the sub panel in the basement. Total run should be around 70 feet. I'll exit the main panel and go up through the side of the house into an LB pull box. I'll then run across the side of the house and down to the basement sub panel where i'll enter the house through another LB pull box and then down into the sub panel. I'll use #6 AWG THWN Cu conductors and a #10 AWG THWN Cu ground. All conduit will be glued in place and allowed to dry prior to pulling wires. Are there any regulations on where you run the conduit, and is there a max pull length before i need another pull box?
 
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Old 05-04-14, 04:01 PM
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That sounds good. No length limit for conduit but total bends can't exceed 360. Depending on expected average load and type of load you might have to increase wire size if it is more than 150 feet.
 

Last edited by ray2047; 05-04-14 at 07:59 PM.
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Old 05-04-14, 06:20 PM
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total bends can't exceed 360
That means between pull points. If you need to exceed 360 degrees, you'll need to add either a pull box or C-fitting as another pull point. There is no limit to the number of bends or degrees in the entire run.
 
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